Intestinal epithelial regenerative capacity: an "Achilles' heel" in trauma/burn/sepsis injuries?

Sepsis: Prognostic Role of Apoptosis Regulators in Gastrointestinal Cells

BACKGROUND

Intestinal epithelial cell apoptosis has been reported in sepsis as a mechanism of organ failure. The aim of this study was to clarify the role of apoptosis-regulating proteins (bcl-2, bax, cytochrome-c, and caspase-8) in septic rats by studying their expression in gastric and intestinal epithelial cells.

METHODS

Adult Wistar rats were subjected to the cecal ligation and puncture (CLP) model of sepsis and randomly divided into two study groups. Sixty-two animals were sacrificed 6, 12, 24, 36, 48, and 60 h post-procedure, and 50 animals served as the survival study group. Sham-operated animals (n = 40) were used as controls. Gastric and intestinal tissue was excised, and immunohistochemical detection of bcl-2, bax, cytochrome-c, and caspase-8 protein expression was performed.

RESULTS

In gastric mucosa, sepsis induced upregulation of bax and downregulation of caspase-8 expression (p = 0.053 and p = 0.05, respectively). Both bax and caspase-8 were upregulated as early as 6 h post CLP and progressively decreased (p = 0.001, p = 0.004 respectively). In contrast, the expression of the anti-apoptotic bcl-2 was upregulated progressively during the sepsis syndrome (p = 0.03). In intestine, sepsis induced a fourfold upregulation of the cytoprotective bcl-2 (p = 0.0001), accompanied by a remarkable increase in bax (p = 0.002) and caspase-8 (p = 0.0001) expression and a decrease in cytochrome-c expression (p = 0.02). The time distribution of the apoptosis regulators followed the same pattern as in gastric tissue, showing an upregulation of the proapoptotic bax and cytochrome c (p = 0.04) during the early phases and a progressively increased expression of bcl-2 during the late phases (p = 0.0001). Bax expression in gastric epithelium of subjects with septic syndrome was detrimental to survival (p = 0.0001), whereas the expression of the cytoprotective bcl-2 in intestinal epithelium appeared to favor a good prognosis (p = 0.0001).

CONCLUSIONS

Sepsis results in alterations of apoptosis regulators in gastrointestinal cells. Alterations of bax and bcl-2 expression in gastric and intestinal epithelial cells may predict the outcome in septic rats.

Improved survival in experimental sepsis with an orally administered inhibitor of apoptosis

The pathophysiology of sepsis involves excessive lymphocyte apoptosis, which correlates with adverse outcomes, and disordered cytokine production, which may promote host injury. As the protease inhibitor (PI) class of antiretroviral agents is known to prevent apoptosis in vitro, we evaluated their effect on survival, lymphocyte apoptosis, and consequent cytokine production in mice with sepsis induced by cecal ligation and perforation. Mice pretreated with PIs have improved survival (67%; P<0.0005) compared with controls (17%) and a significant (P<0.05) reduction in lymphocyte apoptosis. Even mice receiving therapy beginning 4 h after perforation demonstrated improved survival (50%; P<0.05) compared with controls. PI therapy is also associated with an increase in the Th1 cytokine TNF-alpha (P<0.05) early in sepsis and a reduction in the Th2 cytokines IL-6 and IL-10 (P<0.05) late in sepsis; despite no intrinsic antibacterial effects, PI also reduced quantitative bacterial blood cultures. The beneficial effects of PI appear to be specific to lymphocyte apoptosis, as lymphocyte-deficient Rag1-/- mice did not experience benefit from treatment with PI. Thus, inhibition of lymphocyte apoptosis by PI is a candidate approach for the treatment of sepsis.